Okay, I've got the car on ramps and I've eyeballed the block drains. One's a straight shot, the other has an trans line in the way and will probably need an angle joint on it, but no trouble.
I noticed a steady drip from under the car, *behind* the engine. I stuck my hand under it: clear water, which is what's in the system now.
First thought: "Oh, futz. Heater core is dying."
Scooted further in and got a halogen light up in there. The drip is coming from a rubber weep tube beside the transmission. There are two of them; only one is draining.
Any idea what that might be from?